IDC Models has contributed to the development of a new approach to building flow cells for maintaining biological sample integrity during x-ray diffraction.
These new cells, designed by Dr Peter Docker of Diamond Light Source, take advantage of the rapid prototyping (RPT) process, which has enabled the flow cell and all its internal channels and chambers to be included in a single build operation. RPT takes advantage of a turnaround time of days from concept through to testing, with at least an order of magnitude in cost saving. The particular flow cell (shown in figure 1) is to be used in tests where small angle diffraction is measured to give information about proteins.
The protein sample is placed in the small 1mm hole inside the chip (see below).
As the sample is exposed to x-rays, a buffer solution (used to stop the sample degrading) is released from reservoir 1 and flows over the protein sample to reservoir 2. Due to scale, the flow of the buffer is primarily affected by surface area and not (as it would be in the macro world), by volume. This allows devices to be designed to give appropriate flow rates just by altering channel geometry.
A more advanced flow cell is currently being designed which will incorporate a pump (only 7x7x1mm in size) that will allow the buffer solution to be pumped over the sample. Using RPT this integration requires a small alteration to the CAD of the part being reprinted.Working with Diamond Light Source, the UK’s national synchrotron facility, IDC Models used their Viper Stereolithography (SLA) machine, a 3D printer that constructs models by selectively hardening liquid resin, to produce the prototype. The process involves ‘slicing’ a CAD model into cross-sections which are traced by high-power lasers onto the surface of the resin. The resin cures and hardens where it is exposed to the laser, allowing objects to be built up layer by layer. The SLA machine can produce minute components with features sizes of 150µm, in build steps of just 17µm.
The external dimensions of the microchip in figure 1 are just 20 x 12 x 1.5mm. Typical traditional methods of prototyping, including photolithography etching and bonding two halves together, were considered to be time consuming and a costly process considering this microchip is still in its development stage. Having the flexibility of RPT allows for many more iterations and a more organic approach to design. IDC Model’s SLA machine was chosen to produce the prototype as its high degree of accuracy enables Diamond Light Source to understand the chip architecture, where the channels are best positioned and the exact sizing of the chip reservoirs required.
The microchip model is being showcased next month in the States at Nanotech 2013, the world’s largest nanotechnology event, delivering application-focused research from the top international academic, government and private industry labs. We are sure the intricate design of the microchip will interest fellow exhibitors and visitors.